What are the main types of CSS selectors?

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Selectors target which elements a rule applies to. They range from simple (by tag) to powerful combinators. ```css /* Basic selectors */ p { } /* type: all

*/ .card { } /* class: elements with class="card" (reusable) */ #header { } /* id: the one element with id="header" (unique) */ * { } /* universal: every element */ [type="text"]{ } /* attribute: inputs with type=text */ ``` ## Combinators — relationships between elements ```css .menu li { } /* descendant: any li INSIDE .menu (any depth) */ .menu > li { } /* child: only DIRECT children li */ h2 + p { } /* adjacent sibling: the p immediately AFTER an h2 */ h2 ~ p { } /* general sibling: all p siblings after an h2 */ ``` The difference between space (descendant) and `>` (direct child) matters: `.menu li` matches deeply nested `li`s too, while `.menu > li` matches only the top level. ## Pseudo-classes and pseudo-elements ```css a:hover { } /* state: while hovered */ li:first-child { } /* structural: the first li */ li:nth-child(2n){ } /* every even li */ p::first-line { } /* pseudo-element: the first rendered line */ ``` ## Grouping and modern selectors ```css h1, h2, h3 { } /* apply to all three */ :is(h1, h2) a { } /* :is() shortens long selector lists */ .card:has(img) { } /* :has() — a parent that CONTAINS an img */ ``` ## Why it matters Selectors are how you connect styles to markup. Mastering classes (the workhorse), combinators (for relationships), and structural/state pseudo-classes lets you target precisely without adding extra classes everywhere — and modern `:is()`/`:has()` make complex targeting concise. Prefer classes over ids/heavy nesting to keep specificity manageable.